The invention relates to a stereomicroscope.
Stereomicroscopes having a capability for adjusting the stereo base are described in U.S. Pat. No. 3,818,125 (Butterfield, 1971). Although different variations of possibilities for varying the stereo base are described there, such devices have not become widespread in practice. This is in spite of the fact that the disadvantages which are known and specified by Butterfield in the case of stereomicroscopes without stereo base adjustment are still present. To this extent, reference is made to the relevant description parts--in particular in column 2, lines 43-62--in Butterfield, which count as disclosed herein. The reason for not using the teachings of Butterfield apparently lies in various problems which result from his solution proposals. Thus, for example, the use of prisms is excluded (e.g. FIGS. 5-9 in Butterfield), since, as Butterfield himself admits (column 9, lines 65 and 66 of Butterfield), these are accompanied by color aberrations which can have a negative influence on the color quality of the viewed image. The variations proposed by Butterfield having displaceable aperture diaphragms (10, e.g. FIGS. 2 and 5) furthermore have the disadvantage that as a result of a displacement of the latter not only is the stereo base adjusted but in addition the image brightness is darkened or changed, which can disadvantageously lead to too low a light yield, in particular in the case of small stereo bases.
Similar disadvantages occur in the case of the solution proposal in accordance with FIG. 10 of Butterfield. To be specific, as a result of the pivoting of the mirror (50), not only is the stereo base adjusted, but the aperture is also changed, which in turn can lead to corresponding light losses.
The variants proposed by Butterfield according to FIGS. 11 and 12 are in turn complicated and can be implemented only with difficulty to the extent that two parallel lens systems (54) are necessary there, which are associated with a corresponding increase in price and also a corresponding increase in constructional size, with further penalties in terms of light as a result of possibly too small an aperture. Furthermore, it is generally also difficult to adjust such parallel lens systems such that they have identical properties. However, if the properties are not identical, this can lead to fatigue in the observer, in particular if a video camera and monitor are connected in front of said observer, since he does not have the possibility of recorrecting individually, as in the case of two eyepiece beam paths.
It is therefore an object of the present invention to develop a system which, in spite of a variable stereo base, does not reduce the light intensity in the beam path--at least for a certain period and for each beam path separately--by a significant amount. In addition, it is intended to enable recordings--as known per se--using only a single image recording device, for example using a single video camera. Preferably, it is furthermore intended to provide only one main objective and to restrict the constructional size of the stereomicroscope to a minimum.
This object is achieved, for example, by means of the features described herein. As a result of the arrangement of the adjusting device behind the main objective, there is an integrated construction with low light losses and without the disadvantages listed above.
A practical application of the invention results, for example, in the case of video stereomicroscopes.
For such microscopes, but also for other microscopes, a special development of the invention is proposed which can also be applied independently of the invention. To explain the background:
Microscopes often have beam splitters in order to duplicate the beam path directed towards the object to be magnified.
Often provided on split beam paths are, inter alia, additional observer eyepieces, phototubes, camera connections or displays of all types, the images from which are intended to be inserted--that is to say superimposed on the image of the viewed object. This applies in particular also to stereomicroscopes which have an image recording device for producing a stereo view on a 3D display--possibly remote from the microscope.
For the last application, from time to time such an image recording device (e.g. a CCD each) is provided both for the beam path assigned to the left eye and also for the beam path assigned to the right eye.
For the application having the inserted display, in an analogous manner a display (e.g. a CRT each) is provided for the beam path assigned to the left and also to the right eye.
These known stereomicroscopes thus have the disadvantage that two magnification devices (zoom, turret) and two image recording devices or two displays, together with appropriate optics, are necessary. In this case, the left and right image recording devices or optics must be mutually adjusted.
In other known stereomicroscopes there are also solutions having only a single image recording device. There, both the left and the right beam path or the ray bundle located in them are alternately fed to the single image recording device. As a result of such a construction, a second image recording device is saved and, inter alia, the serial recording of a stereoimage pair on one video recording device is facilitated. The changeover process between the two beam paths is in this case achieved using beam splitters and shutters which block off the respective undesired bundle of rays via polarization changes using correspondingly arranged analyzers.
Such a stereomicroscope having geometric superimposition of the right and left frames is described, for example, in U.S. Pat. No. 5,007,715.
The system which is described in U.S. Pat. No. 5,007,715 has the disadvantage that, both during the polarization (about 50%) and during the superimposition (about 50%) of the two polarized bundles of rays by means of a beam splitter, up to 80% of the light intensity which is present of the respective bundles of rays (100%) are lost. A partial superimposition of the two different sets of image information from the right and left image beam paths can make itself noticeable as a further disadvantage if the darkening by the analyzers is not 100%, which can primarily also occur if the polarizers do not operate satisfactorily. Since however it is precisely in microscopes that the brightness on the object to be viewed cannot be arbitrarily increased, the permanent loss in light intensity is disadvantageous. The partial superimposition, on the other hand, can lead to unnecessary stresses for the organs of sight of the observer.
A similar known system is described in U.S. Pat. No. 5,003,385, where likewise about 80% of the light intensity of the left and right beam paths are absorbed before the light is incident on the single camera.
A somewhat different system, where the polarization of the light remains unconsidered, is described in U.S. Pat. No. 5,028,994. There, the light from two first beam paths (left and right beam path) is firstly fed in each case to an LC shutter (twisted nematic type), which can open or close the relevant beam path. The two beam paths are incident--deflected via mirrors--on a beam splitter. If one shutter is open, then the second shutter is closed, for which reason theoretically it is always only possible for light from one of the two first beam paths to arrive at the camera arranged downstream of the beam splitter. At the beam splitter, in each case about 50% of the light intensity is lost; likewise at the shutter, even in the "open condition", about 50% in each case is lost, since the described shutter structure (cf. column 2 line 48 to column 3 line 29) permit only light of a specific polarization direction to pass through. In addition, in the case of the described shutter, the abovementioned disadvantages of partial superimposition may also occur.